This application relates generally to an electrochemical cell or battery, and more specifically relates to a flat, thin, electrochemical cell utilizing a picture frame feature and its method of manufacture, including printing methods. Even more specifically, this invention relates to a thin printable cell comprising two electrodes, a separator, electrolyte, and a cell frame between two laminated film layers, and its method of manufacture.
For the past one hundred years or so, scientists have been making Carbon/Zinc portable power sources for various applications. In the early days of portable power, these power sources were very large compared to today's standards. For example, the very popular “Ignitor Cell” made by Eveready was about 3″ diameter and about 9″ tall and was used in many applications such as radios, buzzers, Xmas lighting, etc. These large cells, as well as some smaller versions, such as the famous Eveready #6 (about 2″ dia.×6″ tall) and the smallest unit cell of the day, the #950 (D size), were commonly made into battery packs with voltages exceeding 40 volts in some applications. These were similar in size, and even larger, than today's car batteries, for uses in lighting devices, radios and car ignition systems. In the mid 1900's, with the advent of advanced electronics such as the transistor, the electrical requirements for portable power sources were drastically reduced. Consequently, cell sizes could also be reduced to include C's, AA's, and AAA's, and even small button cells. This power reduction has continued into the twenty-first century, where applications such as smart labels, smart credit cards, sensors, data loggers, novelty devices such as greeting cards and badges, etc., now require a maximum current of several milliamperes, with many applications requiring as little as a few microamperes at about 1.5-3.0 volts. These applications also have the requirement that the power sources be flat and very thin to maintain their low profiles and portability.
In the past twenty-five years, various approaches for making thin, flat cells and batteries were attempted by numerous scientists and corporations. These include the widely known instant film battery pack developed by Polaroid. This battery pack was used in each package of Polaroid instant film. This allowed Polaroid to have a fresh battery in the camera each time the user placed a new pack of film in the camera. This high cost battery with multiple layers and a metal foil laminate package is a high voltage, high current battery, capable of igniting flash bulbs and powering motors, for example, and is not a realistic competitor of the new thin low cost batteries that are needed. In addition to Polaroid, others have tried to develop thin batteries in various electrochemical systems.
Co-pending application Ser. No. 11/110,202, filed on Apr. 20, 2005, and incorporated herein by reference, discusses a new design and method of manufacture of a flat cell and battery.
With the growing market needs for low cost, low capacity thin flat cells, it would be beneficial to produce a thin, flat, printable flexible cell that is versatile and inexpensive to mass-produce. Printable, disposable thin cells that are well suited for low-power and high-production volume applications would be useful, especially if they offer adequate voltage, sufficient capacity, and low-cost solutions. Conventional low-profile batteries typically have few of these attributes, if any.
Furthermore, a previously described construction in an earlier application, which is assembled using a horizontal pouch filler, (see application Ser. No. 11/110,202, incorporated by reference), may lead to some possible air entrapment, and thus might not be as flat and thin as might be desirable for some applications. Also, such cells disclosed therein may be vulnerable to large compression forces. In addition, it would be useful to avoid the need for the paper layer disclosed in the construction of some embodiments of that application, and furthermore, the liquid electrolyte of that application could prove difficult to handle and may not be printable. It might also be useful to eliminate the folding step disclosed in that application, as well. In addition, a cell that could be integrated into the application it is powering, during manufacture, would be useful as well.